CYCADOFILICALES 



19 



chamber. They could not have been numerous, probably not 

 more than four, judging from the comparative size of the micro- 

 spores. The sperms, as she figures them, are distinctly of the Cycad 

 type, rather than the fern type. Sperms, probably then as now, were 

 such short-lived organisms that their preservation is very surprising. 



The seed. — Fifty years ago, in 

 tracing phylogenies, the greatest 

 gap in the plant kingdom was 

 that between ferns and seed 

 plants; but the discovery of 

 seeds upon leaves which had 

 been assumed to be ferns closed 

 the gap so completely that fern- 

 like leaves, without seeds in or- 

 ganic connection, cannot be as- 

 signed with confidence to either 

 group. The earliest seeds were, 

 doubtless, very small. The best- 

 known of all Carboniferous seeds 

 is Lagenostoma, the seed of Ly- 

 ginopteris (fig. 16). It is small, 

 only 5 or 6 mm. in length; but 

 is already so highly developed 

 that is has progressed a long 

 way in the evolution of the seed. 

 The Mexican god of war, accord- 

 ing to tradition, came into the 



Fig. 15. — Lyginopteris ovoides: section 

 of part of nucellus with pollen chamber 

 containing pollen grains and sperms; nl, 

 part of central core of nucellus; nw, wall of 

 nucellus; p\ p^, p^, and p*, pollen grains; a, 

 sperm; a\ sperm cut across; e, protrusion 

 of endospore; t, tissue, probably fungal; 

 X155. — After Margaret Benson. ^^ 



world, like Minerva, full armed, 

 with a spear in his right hand, a shield in his left, and a crest of green 

 plumes on his head. When that myth originated, the origin of the 

 Cycadofilicales might have been explained in a similar way; but now 

 we feel skeptical in regard to any theory of the origin of the seed 

 which would make it begin with such a highly organized structure 

 as that of Lyginopteris. 



Surrounding the seed is a cupule, fig. 17, which reminds one of the 

 cupules of living forms like Corylus, Fagus, Juglans, and Carya; al- 

 though it must be remembered that in the living forms the cupule 



